Method for making a container with a unitary but removable closure

ABSTRACT

A method and apparatus are provided for molding a container such as an ampoule with a hermetically sealed top or closure joined to the upper portion of the container with a peripheral frangible web. Main mold halves defining a cavity are provided with an inwardly projecting portion that defines an upwardly facing bearing surface and a forming edge. A mandrel is provided with at least a downwardly facing first frustoconical sealing surface and with a frustoconical engaging surface extending downwardly and inwardly from the downwardly facing first frustoconical sealing surface. The mandrel is adapted to be positioned in a length of parison extending from the main mold means to temporarily seal the parison opening during vacuum or blow forming of the container. The parison is engaged and pressed by the mandrel against the main mold means upwardly facing bearing surface to effect a temporary sealing of at least the mandrel against the parison and to effect a compression of the parison between the mandrel and the forming edge of the main mold means to form a reduced thickness section of parison which, upon subsequent retraction of the mandrel means and upon subsequent formation of the sealed top of the container, defines a peripheral frangible web below the sealed container top.

TECHNICAL FIELD

This invention relates to a unitary container, such as a vial orampoule, hermetically sealed with a top or closure structure connectedto the container by means of a frangible web.

BACKGROUND OF THE INVENTION

Hermetically sealed containers with unitary closures are known. Suchcontainers typically have a body portion, a neck portion, and a top orclosure structure to close and seal the opening in the neck portion.

It is also known to provide such containers with means for permittingthe containers to be opened by breaking off the sealed closure at thetop of the container or on the neck portion of the container between thecontainer sealed top and the container body portion.

To facilitate such opening of the container, a frangible web istypically provided in the container neck portion. The frangible webcomprises a reduced thickness region in the wall of the material formingthe neck portion of the container. Such a container is typically openedby twisting or bending the part of the container above the frangible webrelative to the part of the container below the frangible web so as torupture or sever the reduced thickness region of material at thefrangible web.

Containers incorporating the above-described frangible web structure aretypically formed from a thermoplastic material. Such containers areconventionally fabricated by blow molding and/or vacuum forming and mayor may not include an insert article or stopper as part of, or inaddition to, the container sealed top or closure structure.

Tvpically, the thermoplastic material is extruded as a length of parisonin the form of a vertically oriented, elongated, hollow tube between thepair of main mold halves for initially forming the container body withan open top. Means are provided for maintaining the opening at the topof the length of parison in the portion of the parison extendingupwardlv above the main mold means.

An extendable and retractable blowing assembly with a sealing mandreland blowing nozzle is extended into the length of parison in the mainmold halves to temporarily seal the opening. A gas is injected into theparison to mold the container with or without vacuum assist in the moldcavity defined by the main mold halves.

The main mold halves (or other mold members), along with the cooperatingsealing mandrel on the blowing assembly, typically define a structurefor molding the frangible web structure.

One such apparatus for molding and forming a container with a frangibleweb is disclosed and illustrated in U.S. Pat. No. 4,239,726. Withreference to FIG. 6 in that patent, a mandrel 42, which can be equippedwith a container blowing and filling nozzle, is described as beingprovided with an annular, ring-shaped molding surface 42 that serves toform a frangible annular web around the container hollow stem or collet12.

Another apparatus for forming a frangible web in a container isillustrated in U.S. patent application Ser. No. 296,368, filed Aug. 26,1981 and assigned to the assignee of the present invention. Inapplication Ser. No. 296,368, there is disclosed an apparatus formolding a container with a closure article, such as a stopper, insertedin the container opening. The article is disposed within the containeropening by means of a pick up arm that is positioned between the mainmold halves. Sealing mold halves, located above the main mold halves,are subsequently closed to pinch the parison against the pick up armabove the stopper held at the bottom of the pick up arm. The sealingmold halves have an inwardly projecting frangible web forming means orflange for forming the reduced thickness region of the parison to definethe frangible web.

U.S. patent application Ser. Nos. 11,149, filed Feb. 12, 1979, and194,839, filed Oct. 7, 1980, both assigned to the assignee of thepresent invention and both now abandoned, illustrate a molding apparatusfor producing a container. The container has a rigid dispensing tip withan orifice of a predetermined size and has a rigid but hollow capclosing off the orifice. The cap is unitary with, and connected to, thedispensing tip of the nozzle by means of a unitary, annular frangibleweb.

The nozzle of the container described in the above-identified U.S.patent application Ser. Nos. 11,149 and 194,839 is formed in the parisonat the bottom of the main mold halves. The main mold halves have aninterior cavity configuration defining an inwardly projecting flange forcooperating with a ram to form the nozzle and to form the cap structurejoined to the nozzle by means of the annular frangible web.

Finally, U.S. Pat. No. 3,597,793 illustrates an apparatus for molding acontainer and for forming a frangible web in the container. Of interestare the embodiments of the apparatus illustrated in FIGS. 19, 22 and 24.Various forms of a mandrel are shown for cooperating with a pair of mainmold halves.

In FIG. 24 of the patent, the mandrel 130 is illustrated as cooperatingwith the pair of molding jaws 131 to form a weakened, angularly disposedflange 132 between the neck portion 133 of a bottle and the integrallyformed closure top 134.

In FIG. 23 of the patent, a mandrel 127 is illustrated with afrustoconical flange 128 which tapers downwardly and outwardly to form apointed tip 129. The tip 129 cooperates with the tapered surface 126 ofthe molding jaw halves 125 to form a groove at the juncture between theneck portion of a bottle and the closure top to provide a frangible web.

Finally, FIG. 19 of the patent illustrates a mandrel 119 having afrustoconical wall 118 which extends downwardly inwardly away from aflange or pointed tip 114 to provide a groove or frangible web in theparison.

Although the above-described methods and apparatus for forming frangiblewebs in containers function satisfactorily for fabricating frangiblewebs in specific types of containers for which such methods andapparatus were intended, there is no sealing surface within the mainmold that is adequate to withstand gas pressures within the main moldcavity while a container is blow molded therein. It would be desirableto provide an improved method and apparatus for forming frangible websin the neck portion of a container by pressure-assisted molding.

Specifically, it would be desirable to provide improved control of thethickness of the formed frangible web, to provide improved sealingbetween the sealing mandrel and the parison, and to provide a mandrelthat forms, on a consistent and repeatable basis, the frangible web witha smooth surfaced inner wall of a specified diameter.

Further, it would be desirable to provide a method and apparatus whereinthe molding assembly and its maintenance could be simplified to permitthe formation of the frangible web at the top portion of the main moldhalves.

SUMMARY OF THE INVENTION

The present invention provides a method for forming a peripheralfrangible web in the wall of a container molded from a parison ofsemi-soft thermoplastic material in a cavity defined by a pair ofcoacting main mold parts as well as a novel container made by thismethod. The method includes the steps of providing in each of the mainmold parts a protuberance of substantially cuneiform, i.e.,wedge-shaped, cross-section that extends into the mold cavity to form acontinuous circumferential ridge having a peak, and pressing a portionof the semi-soft material against the ridqe to form a peripheralfrangible web having a controlled thickness less than the container wallthickness while providing an effective seal within the main mold topermit the shaping of the container body portion by pressurization fromwithin. Preferably, the semi-soft material is caused to flow across thepeak of the circumferential ridge during the pressing. The presentinvention is particularly well suited for manufacture of hermeticallysealed containers from a relatively tougher or harder thermoplasticmaterial such as polypropylene whose vacuum and/or gas pressure are usedduring the forming process. The containers embodying the presentinvention include a smooth peripheral band on the container inside thatis unitary with the frangible web and defines the inside surfacethereof.

Apparatus for practicing the foregoing method includes (1) main moldmeans defining a mold cavity for initially forming from an extrudedlength of a parison the container body with an open top, (2) means formaintaining an opening at the top portion of the parison that extendsupwardly from the main mold means, (3) an extendable and retractabletemporary sealing assembly that includes means for temporarily sealingthe top opening and for forming a peripheral frangible web in thecontainer below the top opening (i.e., in the sealed portion of theformed container) in cooperation with the main mold means, and (4)sealing mold means operable upon the upwardly extending portion of theparison above the formed frangible web for permanently sealing the topof the formed container after the temporary sealing assembly isretracted.

The apparatus is characterized by main mold means provided with acircumferential portion projecting inwardly into the mold cavity anddefining an upwardly facing bearing surface as well as circumferential,frangible web-forming edge. The main mold means is closable around aportion of the extruded parison length.

The temporary sealing assembly (which may include a blow molding nozzleand/or filling nozzle) is provided with a mandrel having at least (1) adownwardly facing sealing surface and (2) a frustoconical engagingsurface extending downwardly and inwardly from the downwardly facingsealing surface. The mandrel is adapted to be moved so that a pluralityof sealing surfaces engage the parison and press the parison against themain mold surfaces to effect sealing of the mandrel against the parisonand of the parison against the main mold means. This permits formationof the container body by either vacuum molding or by blow moldingwithout gas leakage or blow-by between the mandrel and the parison.

When the mandrel is properly positioned, a predetermined spacing iseffected between the mandrel engaging surface and the forming edge onthe main mold means. The spacing is less than the wall thickness of thecontainer above and below the forming edge of the main mold means. Theforming edge of the main mold means thus cooperates with the mandrelengaging surface to form a reduced thickness section of parison which,upon subsequent retraction of the mandrel, and upon subsequent formationof the permanently sealed top of the container, defines a peripheralfrangible web below the sealed container top.

With this method of forming the frangible web, the thickness of thefrangible web, and the thickness of the walls on either side of thefrangible web, can be more accurately controlled.

Numerous other advantages and features of the present invention willbecome readily apparent from the following detailed description of theinvention, from the claims, and from the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings forming part of the specification, and inwhich like numerals are employed to designate like parts throughout thesame,

FIG. 1 is a side elevational view of a hermetically sealed containerembodying the frangible web and unitary break-off closure fabricated bythe apparatus of the present invention in accordance with the teachingsof the method of the present invention;

FIG. 2 is an enlarged, fragmentary, partial cross-sectional view takengenerally along the planes 2--2 of FIG. 1;

Fiqures 3-6A and FIG. 7 are elevational views, each partly in section,illustrating the apparatus and method of the present invention forforming, filling, and sealing a container;

FIG. 6B is an enlarged view of the upper portion of FIG. 6A showing themandrel configuration in greater detail; and

FIG. 8 is a side elevational view, partly broken away to show interiordetail, of an ampoule embodyinq the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

While this invention is susceptible of embodiment in many differentforms, there is shown in the drawings and will herein be described indetail one specific embodiment, with the understanding that the presentdisclosure is to be considered as an exemplification of the principlesof the invention and is not intended to limit the invention to theembodiment illustrated.

The precise shapes and sizes of the components herein described are notessential to the invention unless otherwise indicated, since theinvention is described with reference to an illustrative embodimentonly.

For ease of description, the method of this invention will be describedwith the apparatus of this invention in a normal operatinq position, andterms such as upper, lower, horizontal, etc., will be used withreference to this normal operating position. It will be understood,however, that the apparatus may be manufactured, transported, stored,and sold in an orientation other than that illustrated.

Referring to FIGS. 1 and 2, the hermetically sealed container withunitary break-off closure of the present invention is designatedgenerally by reference numeral 50 and may have a variety of shapes andsizes. The illustrated container is an example of a particular shapethat includes a generally cylindrical hollow body portion 52 having abottom portion 54 and a top portion 56. The top portion 56 of thecontainer terminates in a sealed top or top closure structure 58.

The container closure structure 58 is designed to be removed from thecontainer to permit the contents to be withdrawn or poured from thecontainer. In the preferred form of the illustrated container, the topclosure structure 58 defines a hollow chamber 59 (FIG. 2 only) and agraspable tab 61 (FIGS. 1 and 2).

The top closure structure 58 seals the opening of the container topportion 56. The closure structure 58 is joined to the container topportion 56 by means of a unitary, annular, frangible web 64 thatcircumscribes the container top portion 56. As best illustrated in FIG.2, the wall thicknesses of the closure structure 58 and of the topportion 56 are greater than the thickness of the peripheral frangibleweb 64. The frangible web 64 defines a locus of potential fracture atwhich the separation of the closure structure 58 from the top portion 56occurs when the container is opened in a manner as is next described indetail. On the container interior the frangible web 64 is defined by asmooth, cylindrical band that is wider than web 64 and on the containerexterior by a notched peripheral segment unitary with top closurestructure 58 and container top portion 56. Preferably the widthdimension of the band is at least about two container wall thicknesses.

To open, the container 50 can be grasped in one hand about the bodyportion 52 and the tab 61 can be grasped between the thumb andforefinger of the other hand. Next, the tab 61 and closure structure 58are twisted or bent downwardly relative to the container top portion 56to cause separation of the closure structure 58 from the top portion 56of the web 64.

Preferably, at least a portion of the container top portion 56 isrelatively rigid compared with the body portion 52 so that themanipulation of the tab 61 and closure structure 58 causes a fracture ofthe frangible web 64 and a complete separation of the closure structure58 from the top portion 56.

The method for forming, filling, and sealing the container 50 will nextbe described with reference to FIGS. 3-7. The apparatus of the presentinvention is illustrated in a simplified form in FIGS. 3-7.

As best illustrated in FIG. 3, the process for forming the container 50with the apparatus of the present invention can be initiated at anextruder head 110 of conventional design. The extruder (not illustrated)and head 110 are adapted to extrude a length of parison 200 in the formof a vertically positioned, elongated, hollow tube of semi-soft moldinggrade thermoplastic material such as low-density polyethylene,high-densitv polyethylene, polypropylene, or the like.

Before, during, or after the parison 200 is extruded to the desiredlength, a mold assembly 300 is positioned in spaced relationship from,and around, the parison 200. This position of the mold assembly 300defines the parison receiving station below the extruder head 110.

The mold assembly 300 includes a lower, first, or main mold meanscomprising mold half 302 and mold half 304 which together define a moldcavity 306, along with associated conventional operating mechanisms (notillustrated). The assembly 300 also includes a pair of two coactingsecond or upper sealing mold halves 308 and 310 and a pair of two vacuumoperable holding jaws 312 and 314.

The first or main mold halves 302 and 304 cooperate, when movedtogether, provide the container body defining cavity 306 for thecontainer 50 (FIGS. 3 and 4). Cavity 306 ultimately serves to define thesidewall of the container body portion 52, the container bottom portion54, the container top portion 56, and a lower portion of the containerclosure structure 58.

In FIG. 3, the first or main mold halves 302 and 304 are shown in anopen position in which they are spaced apart by a distance sufficient topermit the parison 200 to hang between them. The first or main moldhalves 302 and 304 are then moved together from the open positionillustrated in FIG. 3 to a closed position illustrated in FIG. 4 bysuitable operating means, such as by a conventional pneumatic orhydraulic cylinder actuator or actuators (not illustrated). When themain mold halves 302 and 304 are in the closed position illustrated inFIG. 4, the main mold halves 302 and 304 are adapted to form the majorportion of the container 50 as will be described in detail hereinafter.

The second or upper sealing mold halves 308 and 310 may be positioned insliding engagement with the top surfaces of the first or main moldhalves 302 and 304. The second or upper sealing mold halves 308 and 310are preferably mounted or carried by the first or main mold halves 302and 304 and are thus movable with the main mold halves 302 and 304between (1) the main mold open position illustrated in FIG. 3 and (2)the main mold closed position illustrated in FIG. 4.

The upper sealing mold halves 308 and 310 are also capable of movementrelative to the main mold halves 302 and 304. Specifically, when themain mold halves 302 and 304 are in the main mold closed position, thesecond or upper sealing mold halves 308 and 310 can be further movedtogether by suitable conventional actuators (not illustrated) to asealing position (FIG. 7) to form the container closure structure 58 aswill be described in detail hereinafter.

The vacuum operable holding jaws or parison grippers 312 and 314 areadapted to be moved between an extended gripping position and aretracted position. Means for effecting such movement may be providedseparately of the means for moving the first and second mold halves.However, jaws 312 and 314 are preferably mounted for movement with thefirst mold halves 302 and 304. When the first mold halves 302 and 304are in the open position illustrated in FIG. 3, the holding jaws 312 and314 are spaced from the parison 200. When the first mold halves 302 and304 are in the closed position illustrated in FIGS. 4-7, the holdingjaws 312 and 314, having moved with the first or main mold halves 302and 304, are close to the parison and are adapted to engage a portion ofthe parison 200 that extends upwardly above the closed first mold halves302 and 304. The jaws 302 and 314 are constructed to grip the parison200 as a reduced pressure or vacuum is effected by suitable conventionalmeans (not illustrated) between the outer surface of the parison 200 andthe inner surfaces of the holding jaws 312 and 314. The parison 200initially is deformed outwardly to contact the jaws 312 and 314 (asshown in FIG. 5) by means described in detail hereinafter.

When the mold assembly 300 closes about the parison 200 as illustratedin FIG. 4, a portion 204 of the extruded parison projects below thecavity 306 of the first or main mold halves 302 and 304 and forms flashby which the ultimately formed container may be conveyed out of themolding apparatus. The flash may be subsequently severed from, or brokenoff of, the container bottom.

When the first or main mold halves 302 and 304 are in the closedposition illustrated in FIG. 4, the holding jaws 312 and 314 are in thegripping position and ready to engage the upper end of the parison 200that extends above the first and second pairs of mold halves. At thispoint in the process, pressurized air is discharged from the extruderhead 110 through a suitable conventional tube (not illustrated) toexpand the parison slightly so that it comes into contact with theparison grippers or holding jaws 312 and 314 as illustrated in FIG. 5.This parison expansion process is conventional and well known to thoseskilled in the art. The holding grippers 312 and 314, through the vacuumor reduced pressure effected between the outer surface of the parison200 and the inner surfaces of the jaws 312 and 314, maintain an openingin the upper end of the parison 200 when the parison is severed from theextruder.

The parison 200 is severed, as illustrated in dashed lines in FIG. 5,above the holding jaws 312 and 314 and below the extruder head 110, by amoving cutter 320, such as a hot wire, a blade or the like while theupper end of the parison 200 is held and prevented from collapsing bythe holding jaws 312 and 314. Typically, the cutter 320 is maintained atan elevated temperature to aid in passing through and severing theparison 200.

Depending on the container size, a plurality of containers 50 can befabricated at one time in a multi-cavity mold assembly. For ease ofdescription, only one mold cavity is illustrated, however, it is to berealized that the mold assembly 300 may include a plurality of cavitiesaligned in a row and that a plurality of corresponding extruder heads110 may be provided in a row for simultaneously extruding a length ofparison into each such cavity.

The mold assembly 300 is typically mounted on a hydraulically-actuatedmold carriage (not illustrated in the simplified FIGS. 3-7) which movesthe mold assembly, including the holding jaws 312 and 314, into theparison receiving position below the extruder head 110 (FIGS. 3-5). Thecarriage also functions to carry the mold assembly 300, with holdingjaws 312 and 314, from the parison receiving position beneath theextruder head 110 to a position displaced from the extruder head 110where the parison 200 is molded (i.e., blow molded or vacuum-formed)into a container shape, then filled, and finally sealed. This latterposition of the mold assembly 300 is the molding, filling, and sealingstation.

As shown in FIG. 5, typically the mold assembly 300 is moved by the moldassembly carriage (not illustrated) along with holding jaws 312 and 314,away from parison receiving station at the extruder head 110 in adirection normal to the plane of FIG. 5 after the parison 200 has beensevered by the cutter 320. The mold carriage usually moves the moldassembly 300 and the holding jaws 312 and 314 a distance of about 30centimeters to the molding, filling, and sealing station wherein thesevered length of parison is molded, filled and sealed as will next beexplained.

The molding, filling and sealing station is illustrated in FIG. 6A wherethe container 50 is shown as having already been molded and then filledwith a product 51. Molding can be effected by blow molding, vacuumforming, or a combination of both of the foregoing expedients dependingon container size and contour.

At the molding, filling, and sealing station, a vertically reciprocablecomposite mandrel 500 is provided. With the severed parison properlypositioned in the mold assembly at the molding, filling, and sealingstation, the composite mandrel 500 is in registry (or is moved intoregistry) with the opening at the upper end of the severed length of theparison 200. The composite mandrel 500 is then extended downwardly intothe opening of the upper end of the severed length of the parison 200 tourge a portion of the parison 200 against the first or main mold halves302 and 304 as illustrated in FIGS. 6A and 6B so as to temporarily sealthe parison opening and to simultaneously form the peripheral frangibleweb of controlled thickness.

The mandrel 500 preferably includes a conventional blowing tube and aconventional filling tube (neither being visible in FIGS. 6A and 6B).The blowing tube, the filling tube, and the mechanism for moving thecomposite mandrel 500 up and down may be of suitable conventionaldesigns such as those disclosed in the above-discussed U.S. Pat. No.3,919,374 and/or found in commercial machines that incorporate a singlemandrel for molding and filling a container. However, the exterior shapeof the mandrel 500 and the shape of the cooperating adjacent surfaces ofthe mold halves 302 and 304 are of a unique design, discussed in detailhereinafter, to provide a pressure seal during container formation.

If the mandrel includes a blowing tube, compressed gas, such as air,nitrogen, or the like, is discharged through the mandrel blowing tubeinto the interior of the hollow parison to inflate the parison outwardlyagainst the walls of the cavity 306 defined by the first or main moldhalves 302 and 304 with or without vacuum assist through smallpassageways in the molds. The compressed gas is typically discharged forabout one second. The container is formed as a result of the pressuredifferential between the exterior of the parison in the main mold meansand the interior of the parison.

Next, if the container is to be filled with a product, the filling tubeinside the composite mandrel 500 is reciprocated downwardly to open avent passage in the mandrel 500 to permit venting of the compressed gasout of the molded container. Subsequently, the blowing tube is moveddownwardly a small distance within the mandrel 500 so as to open theproduct dispensing valve and to permit the product 51 (FIG. 6A) to beinjected into the formed container from the filling tube.

The product 51 (FIG. 6A), typically a liquid, is usually at a relativelylower temperature than the parison 200 and assists in cooling and thussolidifying the walls of the formed container. After the formedcontainer 50 has been filled with the desired amount of product 51, thecomposite mandrel 500 is withdrawn from the open end of the parison 200.If it is desired to form an unfilled container, the filling procedure,of course, is omitted and the formed container is cooled by thesurrounding mold assembly.

When the composite mandrel 500 has been elevated to a position above theholding jaws 312 and 314, the upper sealing mold halves 308 and 310 areclosed as illustrated in FIG. 7 to form the closure structure 58(including the tab 61). Thus, the filled container 50 becomeshermetically sealed with the unitary closure structure 58.

Subsequently, the sealing mold halves 308 and 310 are opened (along withthe main mold halves 302 and 304 and the holding jaws 312 and 314) topermit removal of the formed, filled, and sealed container 50 from theapparatus (as with an automatic transport device, not illustrated, whichmay grip the flash 204 at the bottom of the container). The flash 204,as well as the extending portion of unmolded parison above the tab 61,may be subsequently severed from, or broken off of, the container 50 bysuitable conventional deflashing techniques.

The novel structure of the mandrel 500 and of the cooperating adjacentsurfaces of the main mold halves 302 and 304 will now be described withreference to FIG. 6B. The mandrel 500 includes a generally cylindricaltube portion 502 which may contain a blowing tube and a filling tubewhich may be of conventional design. The distal end of the cylindricaltube portion 502 has an enlarged collar 504 that serves as a firstsealing element and a frustoconical or tapered engaging surface 506 thatprovides a pressure seal between the mandrel and the parison portionwithin the main mold cavity.

The collar 504 includes a downwardly facing first sealing surface 508having a generally frustoconical shape, a second sealing surface 510also having a generally frustoconical shape, and a frustoconical portion512 joining the top of the second frustoconical sealing surface 510 withthe cylindrical tube portion 502 of the mandrel 500.

The first frustoconical sealing surface 508 faces generally downwardlyand the second frustoconical sealing surface 510 can also becharacterized as facing downwardly, although the inward slant of thesecond frustoconical sealing surface 510 is relatively slight and lessthan the slant of the first frustoconical sealing surface 508.Preferably, the angle between the first frustoconical sealing surface508 and a horizontal plane normal to the longitudinal axis of themandrel 500 is about 15 degrees.

The frustoconical engaging surface 506 extends downwardly and inwardlyfrom the downwardly facing first frustoconical sealing surface 508.Surface 506 engages a sufficient area of the parison as surface 506sweeps past peripheral protuberance 301 to form a pressure seal adequateto maintain desired pressurization in the container body portion duringits formation. The angle of the surface 506 relative to the longitudinalaxis of the mandrel 500 is relatively small. Preferably the anglesformed by the surfaces 506 and 510 relative to the longitudinal axis ofthe mandrel are about equal.

The main sealing mold halves 302 and 304 usually have similar moldsurface configurations and will be described here with respect to mainmold half 302.

Specifically, main mold half 302 is provided with a protuberance 301having a substantially cuneiform or wedge-shaped crossection.Protuberance 301 extends around the periphery of that portion of themold cavity defined by main mold half 302 and into the mold cavity.Protuberance 301, together with a similar protuberance on complementarymain mold half 304 define a continuous circumferential ridge having apeak. The circumferential ridge, in turn, defines an upwardly facingfrustoconical bearing surface 303 and the peak of the ridge defines anannular forming edge 305.

After the mold halves 302 and 304 have been closed (as illustrated inFIG. 6B) about the parison 200 to form the container and the containerbody upper portion 56, the mandrel 500 is moved or extended downwardlyinto the opening of the parison 200 so that the downwardly facing firstfrustoconical sealing surface 508 of the mandrel sealing element 504engages the parison 200 and presses the parison against the upwardlyfacing bearing surface 303 of the main mold halves 302 and 304. Thisaction effects a temporary sealing of the mandrel 500 against theparison 200 and of the parison 200 against the main mold halves 302 and304 to permit subsequent vacuum forming or blow molding of thecontainer.

Preferably, as illustrated in FIG. 6B, the angle of the bearing surface303 relative to a plane normal the longitudinal axis of the mandrel 500is about the same as, if not identical to, the angle of the firstfrustoconical sealing surface 508 with respect to a plane normal to thelongitudinal axis of the mandrel 500. Preferably, this angle is about 15degrees as stated above in describing the orientation of the firstsealing surface 508 of the mandrel 500.

As the mandrel 500 is extended and moved downwardly into the parisonopening, the frustoconical engaging surface 506 engages and slides alongthe parison 200 adjacent the forming edge 305 of the main mold halves302 and 304. This effects sweeping and squeezing of the parison materialin the vicinity of the circumferential ridge and causes the semi-softparison material to flow across the peak of the ridge.

The diameter of the circle defined by the main mold forming edge 305 andthe diameter of the engaging surface 506 adjacent the forming edge 305are such that therebetween there is an annular space sufficient toaccommodate a predetermined thickness of parison which uponsolidification comprises the frangible web designated by referencenumeral 64 in the completed container illustrated in FIGS. 1 and 2.Control of the dimensions of the engaging surface 506 and the formingedge 305 thus permits the fabrication of a frangible web having acontrolled thickness.

In one typical application of this method, the frangible web has athickness of about 0.005 inch (about 0.13 mm) to about 0.01 inch (about0.25 mm) whereas the thickness of the wall above and below the web isabout 0.025 inch (about 0.64 mm) to about 0.03 inch (about 0.76 mm).

It has been found that the above-described novel mandrel structure andmold structure provide a number of benefits and advantages.Specifically, the inwardly tapering configuration of the frustoconicalengaging surface 506 of the mandrel permits a continuous forming andcompression of the parison as the mandrel is extended downwardly intothe parison. Further, the downwardly facing first frustoconical sealingsurface 508 provides for increased positive sealing of the parison tofacilitate subsequent blow forming or vacuum forming of the containerwithin the main mold halves 302 and 304. Also, the location of forminqedge 305 permits more precise position and reduces the likelihood of itsdamage by contact with mandrel 500.

Owing to the inwardly slanting configuration of the frustoconicalsurfaces 506, 508, and 510, retraction of the mandrel 500 causes thesecontacting surfaces to be immediately moved away from the parisonwithout any substantial sliding or dragging contact with the formedparison that may still be in a semi-soft state. Thus, in the criticalfrangible web region, the possibility for disturbing the reducedthickness region of parison adjacent the mold forming edge 305 iseliminated.

With the novel design of the main mold halves 302 and 304 and of themandrel 500, it is relatively easy to control the reduced thickness ofparison comprising the frangible web adjacent the forming edge 305.Further, the capability for repeatedly fabricating containers withsubstantially identical frangible web thicknesses is enhanced. This isimportant where it is desired to produce many containers wherein eachcontainer must be subsequently cleanly severed by application ofsubstantially the same amount of force.

It is also to be realized that with the novel frangible web formingmethod and apparatus herein described, the frangible web can be formedwithin the main mold halves instead of within the sealing molds (such assealing mold halves 308 and 310 in FIGS. 6A and 7). This permits a moresimplified design of the upper sealing mold halves. Further thecapability for maintaining alignment of the mandrel and the main moldhalves is enhanced.

Another type of hermetically sealed container with unitary break-offclosure of the present invention, an ampoule, is illustrated in FIG. 8.In particular, ampoule 450 has body portion 452, bottom portion 454, tip458, and reduced diameter neck portion 456 joining tip 458 and bodyportion 452. In turn, neck portion 456 and tip 458 are joined by meansof unitary peripheral frangible web 464 defined on the ampoule inside bya smooth cylindrical band 465 and on the ampoule outside by notched,peripheral ampoule segment 466 unitary with tip 458 and neck portion456. Cylindrical band 465 is wider than the frangible web 464 andprovides a pressure seal with the sealing surface 506 of mandrel 500 asthe ampoule body portion is formed by pressurization. Preferably, thecylindrical band is of a width equal to at least about two ampoule wallthicknesses.

The ampoule 450 can be fabricated and filled in substantially the samemanner as the container 50 shown in FIGS. 1 and 2 above. To open, theampoule 450 can be held in one hand about its body portion 452 while tip458 is grasped by another hand and severed by fracturing web 464. Aclear separation about the notched segment 466 is obtained without moreeffort.

Numerous variations and modifications may be effected without departingfrom the true spirit and scope of the novel concept of the invention. Itis to be understood that no limitation with respect to the specificapparatus and method illustrated herein is intended or should beinferred. It is, of course, intended to cover by the appended claims allsuch modifications as fall within the scope of the claims.

What is claimed is:
 1. In a method for molding a container from an extruded length of a parison of semi-soft thermoplastic material in the form of a vertically oriented, elongated, hollow tube wherein said method includes the steps of: (A) closing about said parison a main mold means for defining cavity for subsequently forming the container body with an open top, (B) maintaining an opening at the top of the length of parison in a portion of the parison extending upwardly above the closed main mold means, (C) forming a peripheral frangible web in said parison below said top opening and also temporarily sealing the top opening of the parison, (D) molding the container by a pressure differential between the exterior of the parison in said main mold means and the interior of said parison, and (E) thereafter sealing the top of the formed container with a sealing mold, the improvement characterized in thatstep (A) includes providing in said main mold means a circumferential portion that projects inwardly into the cavity and defines a forming edge and an upwardly facing bearing surface; step (C) includes providing a mandrel with a downwardly facing frustoconical sealing surface and a frustoconical engaging surface extending downwardly and inwardly from said sealing surface and extending said mandrel into said parison top opening to (1) force said parison against said main mold means bearing surface with said mandrel sealing surface, and (2) sweep and squeeze said parison adjacent said main mold means forming edge with said mandrel engaging surface; and step (D) includes maintaining said mandrel at a maximum extended position in contact with said parison to (1) effect a temporary seal of said mandrel sealing surface against the parison and of the parison against said closed main mold means bearing surface during molding of the container, and (2) locate said mandrel engaging surface relative to said forming edge of the closed main mold means to retain therebetween a reduced thickness section of a parison whcih, upon subsequent retraction and upon subsequent formation of the sealed top of the container, defines a peripherl frangible web below the sealed container top.
 2. The method in accordance with claim 1 wherein said semi-soft material is caused to flow across said circumferential portion during said step (C).
 3. The method in accordance with claim 1 wherein the peripheral frangible web is formed having a thickness of about 0.005 to about 0.01 inch. 